Power outlet, emissions, fuel flow and water flow based probabilistic control in liquid-fueled gas turbine tuning, related control systems, computer program products and methods

ABSTRACT

Various embodiments include a system having: at least one computing device configured to tune a set of gas turbines (GTs) by performing actions including: commanding each GT in the set of GTs to a base load level, based upon a measured ambient condition for each GT; commanding each GT in the set of GTs to adjust a respective output to match a nominal mega-watt power output value, and subsequently measuring an actual fuel flow value and an actual emissions value for each GT; adjusting at least one of a fuel flow or a water flow for each GT to an adjusted water/fuel ratio in response to the actual emissions value deviating from an emissions level associated with the base load level, while maintaining the respective adjusted output; and adjusting an operating condition of each GT in the set of GTs based upon a difference between the respective measured actual fuel flow value and a nominal fuel flow value at the ambient condition, while maintaining the adjusted water/fuel ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to co-pending U.S. patent application Ser. No.14/546,498, U.S. patent application Ser. No. 14/546,525, U.S. patentapplication Ser. No. 14/546,512, U.S. patent application Ser. No.14/546,520, and U.S. patent application Ser. No. 14/546,491 all filedconcurrently herewith on Nov. 18, 2014.

FIELD OF THE INVENTION

The subject matter disclosed herein relates to tuning and controlsystems. More particularly, the subject matter disclosed herein relatesto tuning and control systems for gas turbines.

BACKGROUND OF THE INVENTION

At least some known gas turbine engines include controllers that monitorand control their operation. Known controllers govern the combustionsystem of the gas turbine engine and other operational aspects of thegas turbine engine using operating parameters of the engine. At leastsome known controllers receive operating parameters that indicate thegas turbine engine's present operating state, define operationalboundaries by way of physics-based models or transfer functions, andapply the operating parameters to the operational boundary models.Additionally, at least some known controllers also apply the operatingparameters to scheduling algorithms, determine error terms, and controlboundaries by adjusting one or more gas turbine engine controleffectors. However, at least some operating parameters may be unmeasuredparameters, such as parameters that may be impractical to measure usingsensors. Some of such parameters include firing temperature (i.e., stage1 turbine vane exit temperature), combustor exit temperature, and/orturbine stage 1 nozzle inlet temperature.

At least some known gas turbine engine control systems indirectlycontrol or monitor unmeasured operating parameters using measuredparameters, such as compressor inlet pressure and temperature,compressor exit pressure and temperature, turbine exhaust pressure andtemperature, fuel flow and temperature, ambient conditions, and/orgenerator power. However, there is uncertainty in the values of indirectparameters, and the associated gas turbine engines may need tuning toreduce combustion dynamics and emissions. Because of the uncertainty ofunmeasured parameters, design margins are used for gas turbine enginesthat include such known control systems. Using such design margins mayreduce the performance of the gas turbine engine at many operatingconditions in an effort to protect against and accommodate worst-caseoperational boundaries. Moreover, many of such known control systems maynot accurately estimate firing temperature or exhaust temperature of thegas turbine engine, which may result in a less efficient engine andvariation from machine-to-machine in facilities with more than one gasturbine engine.

It has proven difficult to reduce variation in firing temperature frommachine-to-machine for industrial gas turbines. For example, firingtemperature is a function of many different variables, includingvariations in the components of the gas turbine and their assembly.These variations are due to necessary tolerances in manufacturing,installation, and assembly of the gas turbine parts. In addition, thecontrols and sensors used to measure the operating parameters of the gasturbine contain a certain amount of uncertainty in their measurements.It is the uncertainty in the measurement system used to sense the valuesof the measured operating parameters and the machine componentvariations that necessarily result in variation of the unmeasuredoperating parameters of the gas turbine engine, such as the firingtemperature. The combination of these inherent inaccuracies makes itdifficult to achieve the design firing temperature of a gas turbineengine at a known set of ambient conditions and results in firingtemperature variation from machine-to-machine.

BRIEF DESCRIPTION OF THE INVENTION

Various embodiments include a system having: at least one computingdevice configured to tune a set of gas turbines (GTs) by performingactions including: commanding each GT in the set of GTs to a base loadlevel, based upon a measured ambient condition for each GT; commandingeach GT in the set of GTs to adjust a respective output to match anominal mega-watt power output value, and subsequently measuring anactual fuel flow value and an actual emissions value for each GT;adjusting at least one of a fuel flow or a water flow for each GT to anadjusted water/fuel ratio in response to the actual emissions valuedeviating from an emissions level associated with the base load level,while maintaining the respective adjusted output; and adjusting anoperating condition of each GT in the set of GTs based upon a differencebetween the respective measured actual fuel flow value and a nominalfuel flow value at the ambient condition, while maintaining the adjustedwater/fuel ratio.

A first aspect includes a system having: at least one computing deviceconfigured to tune a set of gas turbines (GTs) by performing actionsincluding: commanding each GT in the set of GTs to a base load level,based upon a measured ambient condition for each GT; commanding each GTin the set of GTs to adjust a respective output to match a nominalmega-watt power output value, and subsequently measuring an actual fuelflow value and an actual emissions value for each GT; adjusting at leastone of a fuel flow or a water flow for each GT to an adjusted water/fuelratio in response to the actual emissions value deviating from anemissions level associated with the base load level, while maintainingthe respective adjusted output; and adjusting an operating condition ofeach GT in the set of GTs based upon a difference between the respectivemeasured actual fuel flow value and a nominal fuel flow value at theambient condition, while maintaining the adjusted water/fuel ratio.

A second aspect includes a computer program product having program code,which when executed by at least one computing device, causes the atleast one computing device to tune a set of gas turbines (GTs) byperforming actions including: commanding each GT in the set of GTs to abase load level, based upon a measured ambient condition for each GT;commanding each GT in the set of GTs to adjust a respective output tomatch a nominal mega-watt power output value, and subsequently measuringan actual fuel flow value and an actual emissions value for each GT;adjusting at least one of a fuel flow or a water flow for each GT to anadjusted water/fuel ratio in response to the actual emissions valuedeviating from an emissions level associated with the base load level,while maintaining the respective adjusted output; and adjusting anoperating condition of each GT in the set of GTs based upon a differencebetween the respective measured actual fuel flow value and a nominalfuel flow value at the ambient condition, while maintaining the adjustedwater/fuel ratio.

A third aspect includes a computer-implemented method of tuning a set ofgas turbines (GTs), performed using at least one computing device, themethod including: commanding each GT in the set of GTs to a base loadlevel, based upon a measured ambient condition for each GT; commandingeach GT in the set of GTs to adjust a respective output to match anominal mega-watt power output value, and subsequently measuring anactual fuel flow value and an actual emissions value for each GT;adjusting at least one of a fuel flow or a water flow for each GT to anadjusted water/fuel ratio in response to the actual emissions valuedeviating from an emissions level associated with the base load level,while maintaining the respective adjusted output; and adjusting anoperating condition of each GT in the set of GTs based upon a differencebetween the respective measured actual fuel flow value and a nominalfuel flow value at the ambient condition, while maintaining the adjustedwater/fuel ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a schematic illustration of a gas turbine engine (GT),including a control system, according to various embodiments of theinvention.

FIG. 2 shows a schematic view of a control architecture that may be usedwith the control system of FIG. 1 to control operation of the GT,according to various embodiments of the invention.

FIG. 3 shows a graphical depiction of a probabilistic simulation of theoperating states of a statistically significant number of GT engines ofFIG. 1 using a model of the GT used by the control system of FIG. 1.

FIG. 4 shows a flow diagram illustrating a method according to variousembodiments of the invention.

FIG. 5 shows a graphical depiction of a process illustrated in the flowdiagram of FIG. 4, in a two-dimensional Mega-Watt-power v. Fuel Flowgraph.

FIG. 6 shows a graphical depiction of a process illustrated in the flowdiagram of FIG. 4, in a two-dimensional Mega-Watt-power v. Fuel Flowgraph.

FIG. 7 shows a graphical depiction of a process illustrated in the flowdiagram of FIG. 4, in a three-dimensional Mega-Watt-power v. Fuel Flowv. firing temperature (T4) graph.

FIG. 8 shows an illustrative environment including a control systemaccording to various embodiments of the invention.

It is noted that the drawings of the invention are not necessarily toscale. The drawings are intended to depict only typical aspects of theinvention, and therefore should not be considered as limiting the scopeof the invention. In the drawings, like numbering represents likeelements between the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, subject matter disclosed herein relates to tuningand control systems. More particularly, the subject matter disclosedherein relates to tuning and control systems for gas turbines.

Probabilistic control is a methodology for setting the operating stateof a gas turbine (GT) based upon measured output (in mega-watts, MW)mono-nitrogen oxides NO and NO₂ (nitric oxide and nitrogen dioxide),collectively referred to as NO_(x) emissions, and fuel flow. Asdescribed herein, various embodiments provide tuning and control of a GTusing measurements of output and fuel flow. Conventional approachesexist to calculate and tune control mechanisms where measurement errors(output measurements in MW) exist, but no conventional approaches aredesigned to account for and tune GT control functions in view of fuelflow measurements.

As used herein, term P50 GT or P50 machine refers to a mean (or,nominal) gas turbine or similar machine in a fleet. Parametersassociated with this P50 measure are considered ideal, and are rarely ifever attained in an actual gas turbine. Other terms used herein caninclude: a) firing temperature (T4), which is the average temperaturedownstream of a first-stage nozzle, but upstream of the first rotatingbucket in the turbine (e.g., GT); and b) T3.9, which is the combustiontemperature in the gas turbine, and is higher than the firingtemperature. The firing temperature, as is known in the art, cannot bemeasured, but is inferred from other measurements and known parameters.As used herein, the term, “indicated firing temperature” refers to thefiring temperature as indicated by one or more components of controlequipment, e.g., a control system monitoring and/or controlling GTcomponents. The “indicated” firing temperature represents the bestestimate of the firing temperature from conventional sensing/testingequipment connected with the GT control system.

Additionally, as described herein, the term “base load” for a particulargas turbine can refer to the maximum output of the gas turbine at ratedfiring temperature. Further, as described herein, and known in the art,base load for a given gas turbine will change based upon changes inambient operating conditions. Sometimes base load is referred to as“Full Speed Full Load” in the art. Further, it is understood that NOx issensitive to fuel composition, and as such, it is accounted for in anytuning processes conducted in a gas turbine (including tuning processesdescribed herein).

As described herein various processes allow for tuning of a set (e.g.,fleet) of GTs using probabilistic control. The processes adjust theoperation (operating conditions) of each GT in a fleet such that itsoutput (MW), emissions (NOx), true firing temperature (T4) and fuel floware as close as possible to their respective P50 values, reducingvariation across the fleet. However, when a diluent is added, forexample, to control emissions in a liquid-fueled GT, there is an extradegree of freedom in machine operation that can be tuned. Variousembodiments described herein address the extra degree of freedom intuning a liquid-fueled GT.

According to various embodiments, an approach can include the followingprocesses:

1) Commanding one or more gas turbines (e.g., in a fleet) to a designedbase load (MW value, NO_(x) value), based upon a measured ambientcondition. As described herein, in an ideal situation, the GT(s) should,in an ideal scenario, converge to P50 (nominal) operating parameters,including a P50 MW (nominal output) value, a P50 fuel flow value and P50NO_(x) (emissions) value. However, as indicated herein, this does notoccur in real-world operations;

2) Commanding the one or more GTs to adjust its output to match to P50MW (nominal output) value, and measuring the actual fuel flow value(including the diluent flow value) and the actual NO_(x) value for eachGT. It is understood that when a diluent (e.g., water) is introducedinto the fuel flow, that the fuel flow value (flow rate) includes twocomponents: a) a fuel flow rate, and b) a water flow rate, which arebased upon the water/fuel (w/f) ratio in the mixture. That is, while thediluent (e.g., water) flow to a GT is set according to a w/f ratio inthe control system, fuel flow (rate) and water flow (rate) are in factindependent variables. As such, measuring the actual fuel flow valueincludes measuring the diluent flow value, which is a distinct yetcontributing component to the fuel flow value. As noted herein, thisprocess will likely help to bring each GT's actual fuel flow valuecloser to the P50 fuel flow value, but does not fully succeed in thatgoal. Additionally, this output adjustment does not address anotherconcern, that being the elevated firing temperature relative to itsdesired level;

3) Independently adjusting fuel flow and/or water flow for each GT to anadjusted water/fuel (w/f) ratio in response to the actual NOx valuedeviating from the P50 NO_(x) value, while substantially maintaining theMW output of each GT. In various embodiments, this includes modifying anamount of diluent (e.g., water) and/or fuel entering the combustionchamber of the GT, in order to adjust the NO_(x) value to substantiallymeet the P50 NO_(x) value. If the actual NOx value is greater than theP50 NOx value, than the diluent flow rate and fuel flow rate can beiteratively adjusted (e.g., reduce diluent flow rate and increase fluidflow rate) to maintain the P50 MW output level, while decreasing NOx. Ifthe actual NOx value is less than the P50 NOx value, then the diluentflow rate can be increased, with the fluid flow rate decreased), toincrease NOx. This process includes, among other things, maintainingeach GT at its P50 MW value, while establishing a w/f ratio for each GTwhich results in operation at the P50 NOx target. This w/f ratio will bemaintained in subsequent processes, as noted herein; and

4) Adjusting each GT's operating condition based upon its difference(Delta Fuel Flow) between the measured actual fuel flow value (process2) and the expected, P50 fuel flow value for the ambient condition,while maintaining the adjusted w/f ratio. The Delta Fuel Flow value canbe translated to a Delta MW value (representing the difference betweenthe GT's actual output and the P50 MW level) for each GT usingconventional approaches. In this process, each GT that deviates from theP50 MW value, has its operating condition adjusted by a fixed fractionof the Delta MW value (as converted from the Delta NO_(x) value) suchthat it approaches and then reaches the Delta MW value for that GT. Thisadjustment will move each GT onto a line in MW/Fuel Flow space that isorthogonal to the P50 MW/P50 Fuel Flow characteristic for that GT. Theabove-noted general processes are described in further detail herein.

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustration specific example embodiments in which the present teachingsmay be practiced. These embodiments are described in sufficient detailto enable those skilled in the art to practice the present teachings andit is to be understood that other embodiments may be utilized and thatchanges may be made without departing from the scope of the presentteachings. The following description is, therefore, merely illustrative.

FIG. 1 shows a schematic illustration of a gas turbine engine (GT) 10including a control system 18, according to various embodiments. Invarious embodiments, gas turbine engine 10 includes a compressor 12, acombustor 14, a turbine 16 drivingly coupled to compressor 12, and acomputer control system, or controller 18. An inlet duct 20 tocompressor 12 channels ambient air and, in some instances, injectedwater to compressor 12. Duct 20 may include ducts, filters, screens, orsound absorbing devices that contribute to a pressure loss of ambientair flowing through inlet duct 20 and into inlet guide vanes (IGV) 21 ofcompressor 12. Combustion gasses from gas turbine engine 10 are directedthrough exhaust duct 22. Exhaust duct 22 may include sound adsorbingmaterials and emission control devices that induce a backpressure to gasturbine engine 10. An amount of inlet pressure losses and backpressuremay vary over time due to the addition of components to inlet duct 20and exhaust duct 22, and/or as a result of dust or dirt clogging inletduct 20 and exhaust duct 22, respectively. In various embodiments, gasturbine engine 10 drives a generator 24 that produces electrical power.

Various embodiments are described which measure, analyze and/or controla set of GTs, which may include one or more gas turbine engines (GTs),e.g., in a fleet. It is understood that these approaches are similarlyapplied to a single GT as two or more GTs. It is further understood thatthe term “set” as used herein can mean 1 or more.

In various embodiments, a plurality of control sensors 26 detect variousoperating conditions of gas turbine engine 10, generator 24, and/or theambient environment during operation of gas turbine engine 10. In manyinstances, multiple redundant control sensors 26 may measure the sameoperating condition. For example, groups of redundant temperaturecontrol sensors 26 may monitor ambient temperature, compressor dischargetemperature, turbine exhaust gas temperature, and/or other operatingtemperatures the gas stream (not shown) through gas turbine engine 10.Similarly, groups of other redundant pressure control sensors 26 maymonitor ambient pressure, static and dynamic pressure levels atcompressor 12, turbine 16 exhaust, and/or other parameters in gasturbine engine 10. Control sensors 26 may include, without limitation,flow sensors, speed sensors, flame detector sensors, valve positionsensors, guide vane angle sensors, and/or any other device that may beused to sense various operating parameters during operation of gasturbine engine 10.

As used herein, the term “parameter” refers to characteristics that canbe used to define the operating conditions of gas turbine engine 10,such as temperatures, pressures, and/or gas flows at defined locationswithin gas turbine engine 10. Some parameters are measured, i.e., aresensed and are directly known, while other parameters are calculated bya model and are thus estimated and indirectly known. Some parameters maybe initially input by a user to controller 18. The measured, estimated,or user input parameters represent a given operating state of gasturbine engine 10.

A fuel control system 28 regulates an amount of fuel flow from a fuelsupply (not shown) to combustor 14, an amount split between primary andsecondary fuel nozzles (not shown), and an amount mixed with secondaryair flowing into combustor 14. Fuel control system 28 may also select atype of fuel for use in combustor 14. Fuel control system 28 may be aseparate unit or may be a component of controller 18.

Controller (control system) 18 may be a computer system that includes atleast one processor (not shown) and at least one memory device (notshown) that executes operations to control the operation of gas turbineengine 10 based at least partially on control sensor 26 inputs and oninstructions from human operators. The controller may include, forexample, a model of gas turbine engine 10. Operations executed bycontroller 18 may include sensing or modeling operating parameters,modeling operational boundaries, applying operational boundary models,or applying scheduling algorithms that control operation of gas turbineengine 10, such as by regulating a fuel flow to combustor 14. Controller18 compares operating parameters of gas turbine engine 10 to operationalboundary models, or scheduling algorithms used by gas turbine engine 10to generate control outputs, such as, without limitation, a firingtemperature. Commands generated by controller 18 may cause a fuelactuator 27 on gas turbine engine 10 to selectively regulate fuel flow,fuel splits, and/or a type of fuel channeled between the fuel supply andcombustors 14. Other commands may be generated to cause actuators 29 toadjust a relative position of IGVs 21, adjust inlet bleed heat, oractivate other control settings on gas turbine engine 10.

Operating parameters generally indicate the operating conditions of gasturbine engine 10, such as temperatures, pressures, and gas flows, atdefined locations in gas turbine engine 10 and at given operatingstates. Some operating parameters are measured, i.e., sensed and aredirectly known, while other operating parameters are estimated by amodel and are indirectly known. Operating parameters that are estimatedor modeled, may also be referred to as estimated operating parameters,and may include for example, without limitation, firing temperatureand/or exhaust temperature. Operational boundary models may be definedby one or more physical boundaries of gas turbine engine 10, and thusmay be representative of optimal conditions of gas turbine engine 10 ateach boundary. Further, operational boundary models may be independentof any other boundaries or operating conditions. Scheduling algorithmsmay be used to determine settings for the turbine control actuators 27,29 to cause gas turbine engine 10 to operate within predeterminedlimits. Typically, scheduling algorithms protect against worst-casescenarios and have built-in assumptions based on certain operatingstates. Boundary control is a process by which a controller, such ascontroller 18, is able to adjust turbine control actuators 27, 29 tocause gas turbine engine 10 to operate at a preferred state.

FIG. 2 shows a schematic view of an example control architecture 200that may be used with controller 18 (shown in FIG. 1) to controloperation of gas turbine engine 10 (shown in FIG. 1). More specifically,in various embodiments, control architecture 200 is implemented incontroller 18 and includes a model-based control (MBC) module 56. MBCmodule 56 is a robust, high fidelity, physics-based model of gas turbineengine 10. MBC module 56 receives measured conditions as input operatingparameters 48. Such parameters 48 may include, without limitation,ambient pressure and temperature, fuel flows and temperature, inletbleed heat, and/or generator power losses. MBC module 56 applies inputoperating parameters 48 to the gas turbine model to determine a nominalfiring temperature 50 (or nominal operating state 428). MBC module 56may be implemented in any platform that enables operation of controlarchitecture 200 and gas turbine engine 10 as described herein.

Further, in various embodiments, control architecture 200 includes anadaptive real-time engine simulation (ARES) module 58 that estimatescertain operating parameters of gas turbine engine 10. For example, inone embodiment, ARES module 58 estimates operational parameters that arenot directly sensed such as those generated by control sensors 26 foruse in control algorithms. ARES module 58 also estimates operationalparameters that are measured such that the estimated and measuredconditions can be compared. The comparison is used to automatically tuneARES module 58 without disrupting operation of gas turbine engine 10.

ARES module 58 receives input operating parameters 48 such as, withoutlimitation, ambient pressure and temperature, compressor inlet guidevane position, fuel flow, inlet bleed heat flow, generator power losses,inlet and exhaust duct pressure losses, and/or compressor inlettemperature. ARES module 58 then generates estimated operatingparameters 60, such as, without limitation, exhaust gas temperature 62,compressor discharge pressure, and/or compressor discharge temperature.In various embodiments, ARES module 58 uses estimated operatingparameters 60 in combination with input operating parameters 48 asinputs to the gas turbine model to generate outputs, such as, forexample, a calculated firing temperature 64.

In various embodiments, controller 18 receives as an input, a calculatedfiring temperature 52. Controller 18 uses a comparator 70 to comparecalculated firing temperature 52 to nominal firing temperature 50 togenerate a correction factor 54. Correction factor 54 is used to adjustnominal firing temperature 50 in MBC module 56 to generate a correctedfiring temperature 66. Controller 18 uses a comparator 74 to compare thecontrol outputs from ARES module 58 and the control outputs from MBCmodule 56 to generate a difference value. This difference value is theninput into a Kalman filter gain matrix (not shown) to generatenormalized correction factors that are supplied to controller 18 for usein continually tuning the control model of ARES module 58 thusfacilitating enhanced control of gas turbine engine 10. In analternative embodiment, controller 18 receives as an input exhausttemperature correction factor 68. Exhaust temperature correction factor68 may be used to adjust exhaust temperature 62 in ARES module 58.

FIG. 3 is a graph that shows a probabilistic simulation of the operatingstates of a statistically significant number of the gas turbine engine10 of FIG. 1 using the model of gas turbine engine used by controller18. The graph represents power output versus firing temperature of gasturbine engine 10. Line 300 is the linear regression model for theplurality of data points 308. Lines 302 represent the 99% predictioninterval corresponding to data points 308. Further, line 304 representsthe nominal or design firing temperature 50 for gas turbine engine 10,and line 306 represents a nominal or design power output for gas turbineengine 10. In various embodiments, the probabilistic simulation shown inFIG. 3 shows an approximate variance in firing temperature of 80 units.This variance may be attributed to the component tolerances of gasturbine engine 10, and the measurement uncertainty of controller 18 andcontrol sensors 26.

Described herein are approaches for tuning gas turbine engine 10 thatfacilitates reducing variation in the actual gas turbine engine 10operating state, e.g., firing temperature and/or exhaust temperature,which facilitates reducing variation in power output, emissions, andlife of gas turbine engine 10. The probabilistic control approachesdescribed herein may be implemented as either a discrete process to tunegas turbine engine 10 during installation and at various periods, or maybe implemented within controller 18 to run periodically at apredetermined interval and/or continuously during operation of gasturbine engine 10. These approaches do not measure gas turbine firingtemperature directly because firing temperature is an estimatedparameter, as previously discussed. These probabilistic controlapproaches, however, can yield directly measured parameters that arestrong indicators of the firing temperature of the gas turbine engine10, and allow for improved control over the firing temperature in a gasturbine engine 10.

FIG. 4 shows a flow diagram illustrating a method performed according tovarious embodiments. As described herein, the method can be performed(e.g., executed) using at least one computing device, implemented as acomputer program product (e.g., a non-transitory computer programproduct), or otherwise include the following processes:

Process P1: commanding each GT 10 in the set of GTs to a base load level(e.g., target indicated firing temperature), based upon a measuredambient condition for each GT 10. As noted herein, the base load (with atarget indicated firing temp) is associated with a mega-watt poweroutput value and an emissions value for the measured ambient condition.As further noted herein, in response to commanding each GT 10 in the setof GTs to the base load level, each GT 10 does not attain at least oneof the nominal MW output value (P50 MW), the nominal fuel flow value(P50 Fuel Flow) or the nominal emissions value (P50 NO_(x)). Accordingto various embodiments, the process of commanding each GT 10 in the setof GTs to adjust a respective output to match the nominal MW outputvalue moves an actual fuel flow value (as well as emissions value) foreach GT 10 closer to the nominal fuel flow value (and nominal emissionsvalue) without matching the nominal fuel flow value (and nominalemissions value);

Process P2: commanding each GT 10 in the set of GTs to adjust arespective output to match a nominal mega-watt power output value, andsubsequently measuring an actual fuel flow value for each GT 10 and theactual emissions value for each GT 10. As described herein, when adiluent (e.g., water) is introduced into the fuel flow, that the fuelflow value (flow rate) includes two components: a) a fuel flow rate, andb) a water flow rate, which are based upon the water/fuel (w/f) ratio inthe mixture. That is, while the diluent (e.g., water) flow to a GT 10 isset according to a w/f ratio in the control system, fuel flow (rate) andwater flow (rate) are in fact independent variables. As such, measuringthe actual fuel flow value includes measuring the diluent flow value,which is a distinct yet contributing component to the fuel flow value.In various embodiments, process P2 can further include converting thedifference between the respective measured actual fuel flow value andthe nominal fuel flow value for each GT 10 into a difference between arespective mega-watt power output value and the nominal mega-watt poweroutput value at the ambient condition value for each GT 10;

Process P3: Independently adjusting fuel flow and/or water flow for eachGT 10 to an adjusted water/fuel (w/f) ratio in response to the actualemissions value deviating from the nominal emissions value, whilesubstantially maintaining the MW output of each GT 10. In variousembodiments, this includes modifying an amount of diluent (e.g., water)and/or fuel entering the combustion chamber of the GT 10, in order toadjust the emissions value to substantially meet the nominal emissionsvalue. If the actual emissions value is greater than the nominalemissions value, than the diluent flow rate and fuel flow rate can beiteratively adjusted (e.g., reduce diluent flow rate and increase fluidflow rate) to maintain the nominal MW output level, while decreasingemissions. If the actual emissions value is less than the nominalemissions value, than the diluent flow rate can be decreased, with thefluid flow rate increased, to increase emissions. This process includes,among other things, maintaining each GT 10 at its nominal MW outputvalue, while establishing a w/f ratio for each GT 10 which results inoperation at the nominal emissions target. This w/f ratio will bemaintained in subsequent processes, as noted herein; and

Process P4: adjusting an operating condition of each GT 10 in the set ofGTs based upon a difference between the respective measured actual fuelflow value and a nominal fuel flow value at the ambient condition, whilemaintaining the adjusted w/f ratio. According to various embodiments,the process of adjusting the operating condition of each GT 10 includesadjusting the operating condition of each GT 10 in the set of GTs by afixed fraction of the difference between the respective mega-watt poweroutput value and the nominal mega-watt power output value, such that theoutput of each GT 10 approaches and then reaches a respective nominalmega-watt power output value. According to various embodiments,adjusting of the operating condition of each GT 10 in the set of GTs bythe fixed fraction of the difference between the respective mega-wattpower output value and the nominal mega-watt power output value alignseach GT 10 on a line in graphical space plotting mega-watts versusemissions that is orthogonal to a nominal mega-watt power output/fuelflow characteristic for each GT 10.

FIGS. 5-7 show graphical depictions, via MW-power v. Fuel Flow graphs,of the processes described in FIG. 4, with respect to an example dataset representing a set (plurality) of GTs (similar to GT 10). All datapoints shown in FIGS. 5-6 represent MW-power v. Fuel Flow at indicatedfiring temperatures, where “indicated” firing temperature is the firingtemperature as displayed or otherwise outputted by the controller of GT10. That is, the “indicated” firing temperature is not necessarily theactual firing temperature (which, as described herein, cannot beaccurately measured), but instead, the firing temperature as estimatedby the controller (and related equipment) of the GT 10.

As shown in this example, e.g., in FIG. 5, the fleet regression line RLrepresents a conventional statistical regression of the fleet of GTs 10in MW/Fuel Flow space. The line ML is parallel with the Fuel Flow axis(at constant MW), and intersects line RL at the mean data point alongline RL. Line GL is a function of the mean firing temperature (T4) ofthe set of GTs. The mean combustion temperature (T3.9) is a function ofthe mean firing temperature, and is greater than the mean firingtemperature. Noted herein, as the mean firing temperature increases, sowill the mean combustion temperature, meaning that line GL will shift toa greater MW/Fuel Flow value, while remaining orthogonal to line RL. Asdescribed herein, according to various embodiments, a process caninclude shifting line RL, by a particular fraction to determine theposition of GL. In particular, that fraction is measured from theconstant MW line ML, where “0” represents no shift, and “1” representsshifting all GTs 10 in the fleet to the P50 Fuel Flow machine. Accordingto various embodiments, the fraction is determined based upon an amountthat the GT 10 in the fleet of GTs with the highest fuel flow wouldshift in order to move below the P50 Fuel Flow value. In one exampleembodiment shown in FIG. 5, the fraction is approximately 1/1.4 (around0.71). However, it is understood that according to various embodiments,the fraction can vary between approximately 0.5 and 1, e.g., 0.62, 0.8,etc. This shift, performed according to various embodiments, minimizesfuel flow variation across the fleet of GTs 10. It is understood thatthe shifting processes described with respect to FIG. 5 may varydepending upon the type of gas turbine in the fleet of GTs 10. That is,different sized gas turbines, with different ratings, ambientconditions, etc. may require a distinct shift from the constant MW lineML to the ultimate position of GL in order to position the GT with thehighest fuel flow below the P50 Fuel Flow value.

FIG. 6 shows an additional MW/Fuel Flow graphical depiction, withadditional indicates shifted GLs, GL′ and GL″. GL′ shows a shiftfraction of 0.62 (1/1.6) from ML, while GL″ shows a shift fraction of0.8 (1/1.25) from ML.

FIG. 7 shows a three-dimensional graphical depiction of the process P3(FIG. 4), namely, adjusting an operating condition of each GT in the setof GTs based upon a difference between the respective measured actualfuel flow value and a nominal fuel flow value at the ambient condition.That is, as shown in FIG. 7, the GL plane, defined by the plane of theGL (FIGS. 5-6) across firing temperature (T4) space, illustrates a modelof where the set of GTs operate in the firing temperature (T4) space.That is, although actual firing temperature (T4) cannot be directlymeasured for each GT in the set of GTs, the GL plane represents the mostaccurate model of the firing temperature of GTs within the set of GTs.According to the various embodiments, process P3 includes adjusting anoperating condition of each GT based upon a difference between itsrespective measured actual fuel flow value and a nominal (average) fuelflow value for the respective GT. That is, according to variousembodiments, an operating condition of each GT is adjusted such that itsMW/Fuel Flow value intersects GL in two-dimensional space (FIGS. 5-6),and the GL plane in three-dimensional space (FIG. 7). The intersectionof the nominal (P50) MW/Fuel Flow lines and the GL plane represents themost accurate model of the desired mean actual firing temperature (P4),and by tuning each GT 10 to approach that GL plane (described withrespect to FIG. 6), firing temperature variation is reduced across thefleet, increasing the life of the fleet.

The (green line) GL (and the GL plane) is a characteristic of how gasturbines are designed and built, and in MW/Fuel Flow space, its centeris at the intersection of P50 MW and P50 Fuel Flow (and P50 NO_(x)) forthe particular type of GT 10 in a fleet. The length of GL intwo-dimensional space is defined by the GT-to-GT hardware variation fora given type of GT (e.g., physical variances in the manufacture of twomachines to the same specifications). By altering operating conditionsof a GT 10 in order to align the MW/Fuel Flow value for that GT 10 withthe GL (and GL plane), the variation in the actual firing temperature(T4) is minimized.

Additionally, it is understood that the measuring fuel flow as describedherein can be used as a test to determine whether processes of tuning agas turbine, described in accordance with the approaches described inU.S. patent application Ser. No. 14/546,498, are statistically accurate.That is, the MW/NO_(x) space (parameters) determined in accordance withapproaches described in U.S. patent application Ser. No. 14/546,498, canbe compared with the parameters in MW/Fuel Flow space to verify that theMW/NO_(x) values are accurate.

FIG. 8 shows an illustrative environment 802 demonstrating thecontroller (control system 18) coupled with the GTs 10 via at least onecomputing device 814. As described herein, the control system 18 caninclude any conventional control system components used in controlling agas turbine engine (GT). For example, the control system 18 can includeelectrical and/or electro-mechanical components for actuating one ormore components in the GT(s) 10. The control system 18 can includeconventional computerized sub-components such as a processor, memory,input/output, bus, etc. The control system 18 can be configured (e.g.,programmed) to perform functions based upon operating conditions from anexternal source (e.g., at least one computing device 814), and/or mayinclude pre-programmed (encoded) instructions based upon parameters ofthe GT(s) 10.

The system 8042 can also include at least one computing device 814connected (e.g., hard-wired and/or wirelessly) with the control system18 and GT(s) 10. In various embodiments, the computing device 814 isoperably connected with the GT(s) 10, e.g., via a plurality ofconventional sensors such as flow meters, temperature sensors, etc., asdescribed herein. The computing device 814 can be communicativelyconnected with the control system 18, e.g., via conventional hard-wiredand/or wireless means. The control system 18 is configured to monitorthe GT(s) 10 during operation according to various embodiments.

Further, computing device 814 is shown in communication with a user 836.A user 836 may be, for example, a programmer or operator. Interactionsbetween these components and computing device 814 are discussedelsewhere in this application.

As noted herein, one or more of the processes described herein can beperformed, e.g., by at least one computing device, such as computingdevice 814, as described herein. In other cases, one or more of theseprocesses can be performed according to a computer-implemented method.In still other embodiments, one or more of these processes can beperformed by executing computer program code (e.g., control system 18)on at least one computing device (e.g., computing device 814), causingthe at least one computing device to perform a process, e.g., tuning atleast one GT 10 according to approaches described herein.

In further detail, computing device 814 is shown including a processingcomponent 122 (e.g., one or more processors), a storage component 124(e.g., a storage hierarchy), an input/output (I/O) component 126 (e.g.,one or more I/O interfaces and/or devices), and a communications pathway128. In one embodiment, processing component 122 executes program code,such as control system 18, which is at least partially embodied instorage component 124. While executing program code, processingcomponent 122 can process data, which can result in reading and/orwriting the data to/from storage component 124 and/or I/O component 126for further processing. Pathway 128 provides a communications linkbetween each of the components in computing device 814. I/O component126 can comprise one or more human I/O devices or storage devices, whichenable user 836 to interact with computing device 814 and/or one or morecommunications devices to enable user 136 and/or CS 138 to communicatewith computing device 814 using any type of communications link. To thisextent, CC plant load monitoring system 16 can manage a set ofinterfaces (e.g., graphical user interface(s), application programinterface, and/or the like) that enable human and/or system interactionwith control system 18.

In any event, computing device 814 can comprise one or more generalpurpose computing articles of manufacture (e.g., computing devices)capable of executing program code installed thereon. As used herein, itis understood that “program code” means any collection of instructions,in any language, code or notation, that cause a computing device havingan information processing capability to perform a particular functioneither directly or after any combination of the following: (a)conversion to another language, code or notation; (b) reproduction in adifferent material form; and/or (c) decompression. To this extent, CCplant load monitoring system 16 can be embodied as any combination ofsystem software and/or application software. In any event, the technicaleffect of computing device 814 is to tune at least one GT 10 accordingto various embodiments herein.

Further, control system can be implemented using a set of modules 132.In this case, a module 132 can enable computing device 814 to perform aset of tasks used by control system 18, and can be separately developedand/or implemented apart from other portions of control system 18.Control system 18 may include modules 132 which comprise a specific usemachine/hardware and/or software. Regardless, it is understood that twoor more modules, and/or systems may share some/all of their respectivehardware and/or software. Further, it is understood that some of thefunctionality discussed herein may not be implemented or additionalfunctionality may be included as part of computing device 814.

When computing device 814 comprises multiple computing devices, eachcomputing device may have only a portion of control system 18 embodiedthereon (e.g., one or more modules 132). However, it is understood thatcomputing device 814 and control system 18 are only representative ofvarious possible equivalent computer systems that may perform a processdescribed herein. To this extent, in other embodiments, thefunctionality provided by computing device 814 and control system 18 canbe at least partially implemented by one or more computing devices thatinclude any combination of general and/or specific purpose hardware withor without program code. In each embodiment, the hardware and programcode, if included, can be created using standard engineering andprogramming techniques, respectively.

Regardless, when computing device 814 includes multiple computingdevices, the computing devices can communicate over any type ofcommunications link. Further, while performing a process describedherein, computing device 814 can communicate with one or more othercomputer systems using any type of communications link. In either case,the communications link can comprise any combination of various types ofwired and/or wireless links; comprise any combination of one or moretypes of networks; and/or utilize any combination of various types oftransmission techniques and protocols.

As discussed herein, control system 18 enables computing device 814 tocontrol and/or tune at least one GT 10. Control system 18 may includelogic for performing one or more actions described herein. In oneembodiment, control system 18 may include logic to perform theabove-stated functions. Structurally, the logic may take any of avariety of forms such as a field programmable gate array (FPGA), amicroprocessor, a digital signal processor, an application specificintegrated circuit (ASIC) or any other specific use machine structurecapable of carrying out the functions described herein. Logic may takeany of a variety of forms, such as software and/or hardware. However,for illustrative purposes, control system 18 and logic included thereinwill be described herein as a specific use machine. As will beunderstood from the description, while logic is illustrated as includingeach of the above-stated functions, not all of the functions arenecessary according to the teachings of the invention as recited in theappended claims.

In various embodiments, control system 18 may be configured to monitoroperating parameters of one or more GT(s) 10 as described herein.Additionally, control system 18 is configured to command the one or moreGT(s) 10 to modify those operating parameters in order to achieve thecontrol and/or tuning functions described herein.

It is understood that in the flow diagram shown and described herein,other processes may be performed while not being shown, and the order ofprocesses can be rearranged according to various embodiments.Additionally, intermediate processes may be performed between one ormore described processes. The flow of processes shown and describedherein is not to be construed as limiting of the various embodiments.

In any case, the technical effect of the various embodiments of theinvention, including, e.g., the control system 18, is to control and/ortune one or more GT(s) 10 as described herein.

In various embodiments, components described as being “coupled” to oneanother can be joined along one or more interfaces. In some embodiments,these interfaces can include junctions between distinct components, andin other cases, these interfaces can include a solidly and/or integrallyformed interconnection. That is, in some cases, components that are“coupled” to one another can be simultaneously formed to define a singlecontinuous member. However, in other embodiments, these coupledcomponents can be formed as separate members and be subsequently joinedthrough known processes (e.g., fastening, ultrasonic welding, bonding).

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

We claim:
 1. A computing system comprising: at least one computingdevice having at least one controller, the at least one computing deviceconfigured to tune each gas turbine in a set of a plurality of gasturbines based upon a power output parameter, an emissions parameter, awater flow parameter and a fuel flow parameter, wherein the at least onecomputing device is configured to: command each gas turbine in the setto a respective base load level based upon a respective measured ambientcondition; command each gas turbine in the set to adjust a respectiveactual value of the power output parameter of each gas turbine in theset to match a nominal value of the power output parameter of the set,and subsequently measure a respective actual value of the fuel flowparameter and a respective actual value of the emissions parameter foreach gas turbine in the set; perform a first adjustment to at least oneof the respective actual value of the fuel flow parameter or arespective actual value of the water flow parameter for each gas turbinein the set to achieve an adjusted water/fuel ratio in response to themeasured respective actual value of the emissions parameter deviatingfrom a nominal level of the emissions parameter associated with therespective base load level, while maintaining the adjusted respectiveactual value of the power output parameter at the nominal value of thepower output parameter of the set, for each gas turbine in the set; andperform a second adjustment to a respective operating parameter of eachgas turbine in the set based upon a difference between the measuredrespective actual value of the fuel flow parameter and a nominal valueof the fuel flow parameter at the respective measured ambient conditionfor each gas turbine in the set, while maintaining the fuel flowparameter and the water flow parameter at the adjusted water/fuel ratio,wherein the second adjustment to the respective operating parameter ofeach gas turbine in the set aligns each gas turbine in the set onto afirst line in a graphical space plotting the power output parameterversus the fuel flow parameter, wherein the first line is orthogonal toa characteristic line in the graphical space, wherein the characteristicline is a mean characteristic line of all of the plurality of gasturbines in the set, at the respective base load level of each gasturbine in the set, plotting the power output parameter versus the fuelflow parameter.
 2. The computing system of claim 1, wherein therespective base load level is associated with a base load value of thepower output parameter and a base load value of the fuel flow parameterfor the respective measured ambient condition.
 3. The computing systemof claim 1, wherein in response to the command of each gas turbine inthe set to the respective base load level, each gas turbine in the setdoes not attain at least one of: the nominal value of the power outputparameter of the set and the nominal value of the fuel flow parameter atthe respective measured ambient condition.
 4. The computing system ofclaim 1, wherein the at least one computing device is further configuredto convert the difference between the measured respective actual valueof the fuel flow parameter and the nominal value of the fuel flowparameter at the respective measured ambient condition for each gasturbine in the set into a difference between a respective value of thepower output parameter along the first line and the nominal value of thepower output parameter of the set for each gas turbine in the set. 5.The computing system of claim 4, wherein the second adjustment to therespective operating parameter of each gas turbine in the set includesadjusting the respective operating parameter of each gas turbine in theset by a fraction of the difference between the respective value of thepower output parameter along the first line and the nominal value of thepower output parameter of the set, such that the power output parameterof each gas turbine in the set approaches and then reaches a respectivenominal value of the power output parameter along the first line.
 6. Thecomputing system of claim 1, wherein the commanding of each gas turbinein the set to adjust the respective actual value of the power outputparameter of each gas turbine in the set to match the nominal value ofthe power output parameter of the set moves the fuel flow parameter foreach gas turbine in the set closer to the nominal value of the fuel flowparameter at the respective measured ambient condition without matchingthe nominal value of the fuel flow parameter at the respective measuredambient condition.
 7. A computer program product comprising program codeembodied in at least one non-transitory computer readable medium, whichwhen executed by at least one computing device having at least onecontroller, causes the at least one computing device to tune each gasturbine in a set of a plurality of gas turbines based upon a poweroutput parameter, an emissions parameter, a water flow parameter and afuel flow parameter by: commanding each gas turbine in the set to arespective base load level based upon a respective measured ambientcondition; commanding each gas turbine in the set to adjust a respectiveactual value of the power output parameter of each gas turbine in theset to match a nominal value of the power output parameter of the set,and subsequently measuring a respective actual value of the fuel flowparameter and a respective actual value of the emissions parameter foreach gas turbine in the set; performing a first adjustment to at leastone of the respective actual value of the fuel flow parameter or arespective actual value of the water flow parameter for each gas turbinein the set to achieve an adjusted water/fuel ratio in response to themeasured respective actual value of the emissions parameter deviatingfrom a nominal level of the emissions parameter associated with therespective base load level, while maintaining the adjusted respectiveactual value of the power output parameter at the nominal value of thepower output parameter of the set, for each gas turbine in the set; andperforming a second adjustment to a respective operating parameter ofeach gas turbine in the set based upon a difference between the measuredrespective actual value of the fuel flow parameter and a nominal valueof the fuel flow parameter at the respective measured ambient conditionfor each gas turbine in the set, while maintaining the fuel flowparameter and the water flow parameter at the adjusted water/fuel ratio,wherein the second adjustment to the respective operating parameter ofeach gas turbine in the set aligns each gas turbine in the set onto afirst line in a graphical space plotting the power output parameterversus the fuel flow parameter, wherein the first line is orthogonal toa characteristic line in the graphical space, wherein the characteristicline is a mean characteristic line of all of the plurality of gasturbines in the set, at the respective base load level of each gasturbine in the set, plotting the power output parameter versus the fuelflow parameter.
 8. The computer program product of claim 7, wherein therespective base load level is associated with a base load value of thepower output parameter and a base load value of the fuel flow parameterfor the respective measured ambient condition.
 9. The computer programproduct of claim 7, wherein in response to the commanding of each gasturbine in the set to the respective base load level, each gas turbinein the set does not attain at least one of: the nominal value of thepower output parameter of the set and the nominal value of the fuel flowparameter at the respective measured ambient condition.
 10. The computerprogram product of claim 7, which when executed, causes the at least onecomputing device to convert the difference between the measuredrespective actual value of the fuel flow parameter and the nominal valueof the fuel flow parameter at the respective measured ambient conditionfor each gas turbine in the set into a difference between a respectivevalue of the power output parameter along the first line and the nominalvalue of the power output parameter of the set for each gas turbine inthe set.
 11. The computer program product of claim 10, wherein thesecond adjustment to the respective operating parameter of each gasturbine in the set includes adjusting the respective operating parameterof each gas turbine in the set by a fraction of the difference betweenthe respective value of the power output parameter along the first lineand the nominal value of the power output parameter of the set, suchthat the power output parameter of each gas turbine in the setapproaches and then reaches a respective nominal value of the poweroutput parameter along the first line.
 12. The computer program productof claim 7, wherein the commanding of each gas turbine in the set toadjust the respective actual value of the power output parameter of eachgas turbine in the set to match the nominal value of the power outputparameter of the set moves the fuel flow parameter for each gas turbinein the set closer to the nominal value of the fuel flow parameter at therespective measured ambient condition without matching the nominal valueof the fuel flow parameter at the respective measured ambient condition.13. A computer-implemented method of tuning each gas turbine in a set ofa plurality of gas turbines based upon a power output parameter, anemissions parameter, a water flow parameter and a fuel flow parameter,and performed using at least one computing device having at least onecontroller, the computer-implemented method comprising: commanding eachgas turbine in the set to a respective base load level based upon arespective measured ambient condition; commanding each gas turbine inthe set to adjust a respective actual value of the power outputparameter of each gas turbine in the set to match a nominal value of thepower output parameter of the set, and subsequently measuring arespective actual value of the fuel flow parameter and a respectiveactual value of the emissions parameter for each gas turbine in the set;performing a first adjustment to at least one of the respective actualvalue of the fuel flow parameter or a respective actual value of thewater flow parameter for each gas turbine in the set to achieve anadjusted water/fuel ratio in response to the measured respective actualvalue of the emissions parameter deviating from a nominal level of theemissions parameter associated with the respective base load level,while maintaining the adjusted respective actual value of the poweroutput parameter at the nominal value of the power output parameter ofthe set, for each gas turbine in the set; and performing a secondadjustment to a respective operating parameter of each gas turbine inthe set based upon a difference between the measured respective actualvalue of the fuel flow parameter and a nominal value of the fuel flowparameter at the respective measured ambient condition for each gasturbine in the set, while maintaining the fuel flow parameter and thewater flow parameter at the adjusted water/fuel ratio, wherein thesecond adjustment to the respective operating parameter of each gasturbine in the set aligns each gas turbine in the set onto a first linein a graphical space plotting the power output parameter versus the fuelflow parameter, wherein the first line is orthogonal to a characteristicline in the graphical space, wherein the characteristic line is a meancharacteristic line of all of the plurality of gas turbines in the set,at the respective base load level of each gas turbine in the set,plotting the power output parameter versus the fuel flow parameter. 14.The computer-implemented method of claim 13, wherein the respective baseload level is associated with a base load value of the power outputparameter and a base load value of the fuel flow parameter for therespective measured ambient condition.
 15. The computer-implementedmethod of claim 14, wherein in response to the commanding of each gasturbine in the set to the respective base load level, each gas turbinein the set does not attain at least one of: the nominal value of thepower output parameter of the set and the nominal value of the fuel flowparameter at the respective measured ambient condition.
 16. Thecomputer-implemented method of claim 15, further comprising convertingthe difference between the measured respective actual value of the fuelflow parameter and the nominal value of the fuel flow parameter at therespective measured ambient condition for each gas turbine in the setinto a difference between a respective value of the power outputparameter along the first line and the nominal value of the power outputparameter of the set for each gas turbine in the set.
 17. Thecomputer-implemented method of claim 16, wherein the second adjustmentto the respective operating parameter of each gas turbine in the setincludes adjusting the respective operating parameter of each gasturbine in the set by a fraction of the difference between therespective value of the power output parameter along the first line andthe nominal value of the power output parameter of the set, such thatthe power output parameter of each gas turbine in the set approaches andthen reaches a respective nominal value of the power output parameteralong the first line.
 18. The computer-implemented method of claim 13,wherein the commanding of each gas turbine in the set to adjust therespective actual value of the power output parameter of each gasturbine in the set to match the nominal value of the power outputparameter of the set moves the fuel flow parameter for each gas turbinein the set closer to the nominal value of the fuel flow parameter at therespective measured ambient condition without matching the nominal valueof the fuel flow parameter at the respective measured ambient condition.